Prepare the Oven and Baking Dish: Preheat your oven to 350°F (175°C). Grease or line an 8x8-inch baking dish with parchment paper, ensuring some overhang for easy removal.

Make the Crust and Crumb Topping: In a large mixing bowl, combine the flour, coconut, sugar, baking soda, baking powder, and salt. Add the melted butter and mix until crumbly. Reserve 1 cup of the mixture for the topping and press the remaining mixture evenly into the bottom of the prepared baking dish to form the crust.

Prepare the Filling: In a medium saucepan, combine the crushed pineapple (with juice), sugar, and cornstarch. Cook over medium heat, stirring constantly, until the mixture thickens and becomes glossy (about 3-5 minutes). Remove from heat and let cool slightly.

Assemble the Bars: Pour the pineapple filling evenly over the crust in the baking dish. Sprinkle the reserved crumb mixture evenly over the top.

Bake: Bake in the preheated oven for 30-35 minutes, or until the top is golden brown and the filling is bubbling around the edges.

Cool and Slice: Allow the bars to cool completely in the baking dish. Once cooled, use the parchment overhang to lift the bars out of the dish. Slice into squares or bars and serve.